[Boatanchors] Tube Oscillator Circuit Question

[Richard Knoppow]

    I pass this along without knowing what the circuit looks 
like. In the Hammarlund SP-600 the BFO has a buffer which feeds 
the detector. I found if I look at the BFO waveform at the BFO or 
the grid of the buffer it looks distorted but at the plate of the 
buffer it looks fine. Some sort of loading there. This was with a 
Tek scope and I think a 10X probe. My first thought was that the 
BFO was broken and then realized it was an artifact of the way it 
was being measured. Perhaps you are encountering the same sort of 
thing.

On 12/13/2020 10:02 AM, whitebear1122 at comcast.net wrote:
> I am working on resolving one of the two remaining issues with my HBR-13 12
> tube dual conversion superhet receiver.  The receiver works but the BFO
> waveform has bothered me since I built it.
>
>   
>
> The output of the oscillator is not a nice sine wave as I was expecting.
> The photo shows the oscilloscope at the oscillator plate pin 5.  Amplitude
> is about 96 volts p-p.  I pulled the tube to measure DC voltage applied to
> pin 5 and 6,  151v.  The waveshape on the tuned circuit side pins 1 and 2
> looks good, a normal sine wave.  I just don't know what I'm seeing.  Any
> advice is appreciated.  Thanks. 73, Scott WA9WFA
>
>

-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL